Disclosed are methods for treating neurodegenerative diseases such as Amyotrophic Lateral Sclerosis, Alzheimer's Disease, Parkinson's Disease, Myasthenia Gravis, Multifocal Motor Neuropathy, Primary Lateral Sclerosis, Spinal Muscular Atrophy, Kennedy's Disease, and Spinocerebellar Ataxia, by administration of a compound that blocks the interaction of CD40 and CD40L.